Fig. 6. Both FH1 and FH2 domains of Fhos are required for promoting actin fiber formation, but the FH1 domain is dispensable for homotypic complex formation. (A) The structure of Fhos and its FH1- or FH2-truncated mutant proteins. (B) HeLa cells were transfected with vectors encoding the indicated Fhos truncation mutants. Cells were fixed and then detected by GFP fluorescence (left panels) or phalloidin staining (right panels). Bar, 20 µm. (C) HeLa cells expressing Myc-tagged Fhos mutants were lysed and immunoprecipitated with the anti-Myc antibody. The immunoprecipitates were blotted with anti-Fhos or anti-Myc antibodies. Proteins in cell lysates were also analyzed directly by immunoblot.